Program Information
Improve the Dosimetric Outcome in Treating Bilateral Head and Neck Cancer Treatment Using a Novel Robust and Delivery Efficient Spot Scanning Proton Arc Therapy: A Feasibility Study
X Ding*, A Qin , X Li , J Zhou , C Stevens , D Krauss , P Kabolizadeh , D Yan , William Beaumont Hospital, Royal Oak, MI
Presentations
TH-AB-605-5 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 605
Purpose: Spot-scanning proton arc therapy(SPArc) is a novel planning and treatment technique which has the potential to deliver a robust proton beam therapy through arc trajectories continuously and efficiently. This is the first study to evaluate its feasibility to improve the dosimetric outcome in treating bilateral head and neck cancer(HNC) patients over the traditional robust optimized intensity modulated proton therapy(ro-IMPT) with limited beam angles.
Methods: Ten HNC patients were retrospectively included in this study. Both SPArc and ro-IMPT plans were generated using robust optimization with ±3.5% range and 3mm setup uncertainties in which SPArc plans utilize a full arc with 2.5 degree sampling frequency and ro-IMPT plans utilize three beam angles. The prescription dose is 7000cGy for high-risk clinical target volume(CTV1) and 6000cGy for lymph nodes(CTV2_nodes). Dosimetric parameters were extracted and compared between the two groups. Root-mean-square deviation doses (RMSDs) Volume Histogram, or RVH, and worst-case-scenario perturbed dose volume histogram were used for plan robustness evaluation. Total beam delivery time was compared based on a full gantry rotation with 1RPM, 2ms spot switching time simulating different proton systems with energy-layer-switching-time(ELST) from 0.1 to 5 seconds.
Results: SPArc had demonstrated significant dosimetric improvements over ro-IMPT plans by reducing 28.0%, 30.8% and 35.5% of mean dose to the ipsilateral parotid (p<0.001), contralateral parotid (p<0.001), and oral cavity (p<0.001) respectively. The D1 of brain stem also reduced by a factor of 22.5% (p=0.004). RVH and perturbed DVH analysis shows that plan robustness of SPArc is comparable to ro-IMPT in OARs and target coverage. The average total estimated beam delivery of SPArc plans could potentially achieve less than 500s in the modern proton machine with ELST less than 1s.
Conclusion: This study demonstrated that SPArc could significantly reduce dose to the critical organ dose and has the potential to be implemented in routine clinic.
Funding Support, Disclosures, and Conflict of Interest: Xuanfeng Ding; Xiaoqiang Li and Di Yan are the inventor of Spot-scanning arc therapy
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